Other Forms of Thalassaemia & Abnormal Haemoglobins

Other Forms of Thalassaemia & Abnormal Haemoglobins

Like the β-thalassaemia carrier, the δβ-thalassaemia carrier is a healthy individual and needs no medical treatment. A child however, inheriting either one δβ-thalassaemia gene from each δβ-carrier parent (i.e. δβ/ δβ ) or one δβ-halassaemia gene from one parent and one β-thalassaemia gene from the other parent (i.e. δβ / β) will develop a severe haemoglobin disorder, similar in its clinical outcome to β-thalassaemia major or β-thalassaemia intermedia, and will thus require similar clinical management.
A number of “abnormal” types of adult haemoglobin have been identified, which differ both in their structure and clinical outcome. These are also known as “structural haemoglobin variants” and include HbS, which is the haemoglobin responsible for sickle cell disease (SCD), haemoglobin E (HbE), haemoglobin C (HbC), haemoglobin D (HbD) and haemoglobin Lepore (Hb Lepore). These are passed on from parents to their children and are inherited in exactly the same way as β-thalassaemia. However, only those individuals that inherit from both parents Hb Lepore (i.e. Hb Lepore/ Hb Lepore ) or HbS (i.e. HbS/ HbS) will develop clinically significant conditions that require medical care. These conditions are described in another section on sickle cell disease syndromes. Inheritance of the other abnormal haemoglobins, i.e. HbC, or HbD or HbE from both parents is not related to any significant clinical outcome, and so these do not require any medical attention. However, inheritance of an ”abnormal” haemoglobin, Lepore, E or S from one parent and β-thalassaemia from the other parent results in compound haemoglobinopathies, such as Hb Lepore/β, HbE/β, and HbS/β, which are clinically significant blood disorders similar to β-thalassaemia major/intermedia or Sickle cell disease and require appropriate medical care. More details associated with the most common of the “abnormal” haemoglobins, HbE, are provided below.
HbE is one of the most common abnormal haemoglobin variants, particularly prevalent amongst people of South East Asian origin. Like the β-thalassaemia carrier, the HbE carrier is a healthy individual and needs no medical treatment. However, the non-functional HbE-globin gene can be passed on from the parent to his/her children according to the inheritance pattern described earlier for β-thalassaemia. A child inheriting two HbE genes, one from each of his/her parents (i.e. HbE/HbE), will still be healthy and not require medical care. HbE becomes important only when the child inherits from one parent the β-thalassaemia gene (i.e. one non-functional β-globin gene) and from the other parent the HbE-globin gene (i.e. HbE/ β), as seen in the diagram below. This will result in HbE/β-thalassaemia which is a serious disorder, the clinical symptoms of which are similar to those seen in β-thalassaemia intermedia, but which may sometimes be as severe as those seen in thalassaemia major. This condition will also be further discussed under the section ‘Non-Transfusion Dependent Thalassaemias (NTDTs)’. 1444660082haemoglobin-e-hbe